Self-cleaning and spectrally selective coating on cotton fabric for passive daytime radiative cooling

Passive daytime radiative cooling (PDRC) materials have attracted increasing attention because of the potential in energy saving and the possibility to meet the need of smart clothes. In this work, we fabricate a multifunctional cotton fabric for radiative outdoor cooling using spectrally selective aluminum phosphate particles. The fabric is further modified to be superhydrophobic by introducing a polydimethylsiloxane (PDMS) layer, with the water contact angle (WCA) of 151.9 +/- 0.9 degrees and the sliding angle of 1.3 +/- 0.3 degrees. By reflecting the sunlight (the reflectivity is near 90%) and radiating the heat to the outer space (the emissivity is about 0.92) of the coating, this cotton fabric can reach an average temperature drop of similar to 5.4 degrees C compares to the bare cotton, and enable human body to avoid overheating by 1.0 degrees C similar to 4.4 degrees C under direct sunlight. After 20 times washing, the WCA decreases slightly from 151.9 degrees to 143.9 degrees while the sliding angle of water increases from 1.3 degrees to 5.3 degrees, the cooling temperature still remanins similar to 4.2 degrees C, demonstrating great washing durability of the prepared cotton fabric. Owing to these superior capability and simple production, this superhydrophobic textile for passive daytime radiative cooling is promising to be widely used in outdoor coats and other facilities.